Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753216AbaLJBFa (ORCPT ); Tue, 9 Dec 2014 20:05:30 -0500 Received: from mail-ie0-f177.google.com ([209.85.223.177]:35094 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752574AbaLJBF3 (ORCPT ); Tue, 9 Dec 2014 20:05:29 -0500 MIME-Version: 1.0 In-Reply-To: References: <1417702295-11001-1-git-send-email-ruiv.wang@gmail.com>

Date: Tue, 9 Dec 2014 20:05:21 -0500 Message-ID: Subject: Re: [PATCH] drm: fb helper should avoid sleeping in panic context From: Rob Clark To: rui wang Cc: "airlied@redhat.com" , Daniel Vetter , tony.luck@intel.com, bp@alien8.de, aris@redhat.com, rui.y.wang@intel.com, "dri-devel@lists.freedesktop.org" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org oh, whoops.. gmail hiding quoted text.. yeah, that looks sane, Reviewed-by: Rob Clark On Tue, Dec 9, 2014 at 7:55 PM, rui wang wrote: > Hi Rob, > Yes it's exactly what I'm doing. Please scroll down and review my patch. > > Thanks > Rui > > On 12/10/14, Rob Clark wrote: >> perhaps fb helpers could use __drm_modeset_lock_all() w/ trylock=true >> in panic context? >> >> BR, >> -R >> >> On Tue, Dec 9, 2014 at 7:09 PM, rui wang wrote: >>> Hi All, >>> >>> Any comment ? Or any better idea how this should be fixed? >>> >>> Regards, >>> Rui >>> >>> ---------- Forwarded message ---------- >>> From: ruiv.wang@gmail.com >>> Date: Thu, 4 Dec 2014 22:11:35 +0800 >>> Subject: [PATCH] drm: fb helper should avoid sleeping in panic context >>> To: airlied@redhat.com, daniel.vetter@ffwll.ch, tony.luck@intel.com, >>> bp@alien8.de, aris@redhat.com, rui.y.wang@intel.com >>> Cc: linux-kernel@vger.kernel.org >>> >>> From: Rui Wang >>> >>> There are still some places in the fb helper that need to avoid >>> sleeping in panic context. Here's an example: >>> >>> [ 65.615496] bad: scheduling from the idle thread! >>> [ 65.620747] CPU: 92 PID: 0 Comm: swapper/92 Tainted: G M E >>> 3.18.0-rc4-7-default+ #20 >>> >>> [ 65.630364] Hardware name: Intel Corporation BRICKLAND/BRICKLAND, >>> BIOS BRHSXSD1.86B.0056.R01.1409242327 09/24/2014 >>> [ 65.641923] ffff88087f693d80 ffff88087f689878 ffffffff81566db9 >>> 0000000000000000 >>> [ 65.650226] ffff88087f693d80 ffff88087f689898 ffffffff810871ff >>> ffff88046eb3e0d0 >>> [ 65.658527] ffff88087f693d80 ffff88087f6898c8 ffffffff8107c1fa >>> 000000017f6898b8 >>> [ 65.666830] Call Trace: >>> [ 65.669557] <#MC> [] dump_stack+0x46/0x58 >>> [ 65.675994] [] dequeue_task_idle+0x2f/0x40 >>> [ 65.682412] [] dequeue_task+0x5a/0x80 >>> [ 65.688345] [] deactivate_task+0x23/0x30 >>> [ 65.694569] [] __schedule+0x580/0x7f0 >>> [ 65.700502] [] schedule_preempt_disabled+0x29/0x70 >>> [ 65.707696] [] __ww_mutex_lock_slowpath+0xb8/0x162 >>> [ 65.714891] [] __ww_mutex_lock+0x53/0x85 >>> [ 65.721125] [] drm_modeset_lock+0x3d/0x110 [drm] >>> [ 65.728132] [] __drm_modeset_lock_all+0x8a/0x120 >>> [drm] >>> [ 65.735721] [] drm_modeset_lock_all+0x10/0x30 [drm] >>> [ 65.743015] [] >>> drm_fb_helper_pan_display+0x2f/0xf0 [drm_kms_helper] >>> [ 65.751857] [] fb_pan_display+0xd1/0x1a0 >>> [ 65.758081] [] bit_update_start+0x20/0x50 >>> [ 65.764400] [] fbcon_switch+0x3a2/0x550 >>> [ 65.770528] [] redraw_screen+0x189/0x240 >>> [ 65.776750] [] fbcon_blank+0x20a/0x2d0 >>> [ 65.782778] [] ? erst_writer+0x209/0x330 >>> [ 65.789002] [] ? internal_add_timer+0x63/0x80 >>> [ 65.795710] [] ? mod_timer+0x127/0x1e0 >>> [ 65.801740] [] do_unblank_screen+0xa8/0x1d0 >>> [ 65.808255] [] unblank_screen+0x10/0x20 >>> [ 65.814381] [] bust_spinlocks+0x19/0x40 >>> [ 65.820508] [] panic+0x106/0x1f5 >>> [ 65.825955] [] mce_panic+0x2ac/0x2e0 >>> [ 65.831789] [] ? delay_tsc+0x4a/0x80 >>> [ 65.837625] [] do_machine_check+0xbaf/0xbf0 >>> [ 65.844138] [] ? intel_idle+0xc7/0x150 >>> [ 65.850166] [] machine_check+0x1f/0x30 >>> [ 65.856195] [] ? intel_idle+0xc7/0x150 >>> [ 65.862222] <> [] >>> cpuidle_enter_state+0x55/0x170 >>> [ 65.869823] [] cpuidle_enter+0x17/0x20 >>> [ 65.875852] [] cpu_startup_entry+0x2d8/0x370 >>> [ 65.882467] [] start_secondary+0x159/0x180 >>> >>> There's __drm_modeset_lock_all() which Daniel Vetter introduced for this >>> purpose. We can leverage that without reinventing anything. This patch >>> works with the latest kernel. >>> >>> Signed-off-by: Rui Wang >>> --- >>> drivers/gpu/drm/drm_fb_helper.c | 8 ++++++-- >>> 1 files changed, 6 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/drm_fb_helper.c >>> b/drivers/gpu/drm/drm_fb_helper.c >>> index 0c0c39b..70dd2f4 100644 >>> --- a/drivers/gpu/drm/drm_fb_helper.c >>> +++ b/drivers/gpu/drm/drm_fb_helper.c >>> @@ -732,7 +732,9 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, >>> struct fb_info *info) >>> int i, j, rc = 0; >>> int start; >>> >>> - drm_modeset_lock_all(dev); >>> + if (__drm_modeset_lock_all(dev, !!oops_in_progress)) { >>> + return -EBUSY; >>> + } >>> if (!drm_fb_helper_is_bound(fb_helper)) { >>> drm_modeset_unlock_all(dev); >>> return -EBUSY; >>> @@ -910,7 +912,9 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo >>> *var, >>> int ret = 0; >>> int i; >>> >>> - drm_modeset_lock_all(dev); >>> + if (__drm_modeset_lock_all(dev, !!oops_in_progress)) { >>> + return -EBUSY; >>> + } >>> if (!drm_fb_helper_is_bound(fb_helper)) { >>> drm_modeset_unlock_all(dev); >>> return -EBUSY; >>> -- >>> 1.7.5.4 >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" >>> in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> Please read the FAQ at http://www.tux.org/lkml/ >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" >>> in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> Please read the FAQ at http://www.tux.org/lkml/ >> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/